console: Add ANSI escape sequences for highlighting

This patch adds ANSI escape sequences to highlight a log line based on
its loglevel to the output of "interactive" consoles that are meant to
be displayed on a terminal (e.g. UART). This should help make errors and
warnings stand out better among the usual spew of debug messages. For
users whose terminal or use case doesn't support these sequences for
some reason (or who simply don't like them), they can be disabled with a
Kconfig.

While ANSI escape sequences can be used to add color, minicom (the
presumably most common terminal emulator for UART endpoints?) doesn't
support color output unless explicitly enabled (via -c command line
flag), and other terminal emulators may have similar restrictions, so in
an effort to make this as widely useful by default as possible I have
chosen not to use color codes and implement this highlighting via
bolding, underlining and inverting alone (which seem to go through in
all cases). If desired, support for separate color highlighting could be
added via Kconfig later.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I868f4026918bc0e967c32e14bcf3ac05816415e8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61307
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

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